Prenatal Sonographic Features of Trisomy 13

Fetuses with trisomy 13 are characterized by many associated congenital anomalies including defects of the brain, face, heart, and limbs. The complex anomalies usually result in early embryo death or intrauterine fetal death in the late stages. Only 5-10% of live births have a longer survival time after delivery but these patients are often mentally retarded. Prenatal sonography has been reported to detect more than 90% of trisomy 13 fetuses with major structural defects in the second trimester. In recent years, the addition of soft markers to the sonographic screening for fetal trisomy 13 in the first trimester has been significantly beneficial. This article provides an overview of the common sonographic features of fetal trisomy 13 with major structural abnormalities including brain defects, midline facial defects, cardiac anomalies, genitourinary anomalies, limb anomalies and abdominal wall defects, and minor structural abnormalities including increased nuchal translucency thickness, echogenic intracardiac focus, fetal tachycardia, and megacystis. Several diseases may have phenotypic overlaps with trisomy 13 syndrome including Meckel-Gruber syndrome, pseudotrisomy 13 syndrome, Smith-Lemli-Opitz syndrome, Pallister-Hall syndrome, and hydrolethalus syndrome. Due to the seriousness of this congenital anomaly, increased understanding of the different sonographic markers will improve the detection of trisomy 13 and prenatal ultrasound is a valuable tool in detecting a variety of congenital structural malformations of this lethal syndrome throughout gestation.